2 cell holder case for 21700/18650 - XT30 connector

This is a little design I made to extend the meagre battery life of my BetaFPV VR03 goggles. It's a sturdy, closed design, it clamps down tightly thanks to the M3 screw, it's reasonably compact and easy to build. It's easy to carry too without worrying about it opening or the cells falling: the tolerances are tight enough to avoid any play. As you can see in the pics, it's flat design makes it appropriate to stick velcro strips to it, so it can be easily attached to anything.

Note: this is not suited for high current applications. It's a holder, and the cells and nickel strips make contact through sheer mechanical pressure.

Materials needed

• 1 x M3 heat insert
• 1 x M3*10 screw
• 2 x 50*8mm nickel strip
• 1 x XT30 female

Printing

Both design should print well when oriented vertically and on their flat end. For the body, you may need minimal tree supports in the bottom, for the connector cavity's top part.

Honestly, the print settings are not too relevant, just make sure you have decent bridges and use whatever works for you. I printed mine in PETG, using 2 walls and 20% gyroid infill. No special reasons, I just like it that way.

Build instructions

1. Cut the body's top “supports” as indicated in the attached photo. Now that I think, this step may not be even necessary, but that's how I did it.
2. Set the heat insert in the hole at the top of the body part. Push it all the way down.
3. Install the bottom nickel strip. For that, you push it through the gap that looks like it's only there for the nickel strip, and once you have it centered, fold the extremes upwards. There you have your bottom contact. It's best to solder one wire to the strip now, you have just enough space. It will be harder later.
4. Install the top nickel strip. This one is easier, no pushing through gaps. What I did is I soldered one extreme of a wire in the middle of the strip, then glued it to the top part of the body, and folded the extremes downwards.
5. Install the XT30 connector. The easiest way, I found out, is to pass the free end of the two wires through the hole in the bottom of the body, solder them to the connector, and then push the connector into place. You have enough space to just stuff the few centimeters of loose wire into the gap around the connector.
6. When you put the cells into place, you'll see the top tabs bend and now portrude a little upwards. This is by design. Now you can push the cover onto the assembled body, and secure it with a M3 screw. You can shake it, it ain't going nowhere.